Dgman is a schema manager for Dgraph using the Go Dgraph client (dgo), which manages Dgraph types, schema, and indexes from Go tags in struct definitions, allowing ORM-like convenience for developing Dgraph clients in Go.

Features

• Create types (Dgraph v1.1+), schemas, and indexes from struct tags.
• Detect conflicts from existing schema and defined schema.
• Mutate Helpers (Create, Update, Upsert).
• Autoinject node type from struct.
• Field unique checking (e.g: emails, username).
• Query helpers.
• Delete helper.

Roadmap

• Query builders
• Query fragments

Table of Contents

• Installation
• Usage
  • Schema Definition
    • Node Types
    • CreateSchema
    • MutateSchema
  • Mutate Helpers
    • Mutate
    • Create (Mutate with Unique Checking)
    • Upsert
    • Create Or Get
    • Update On Conflict
  • Query Helpers
    • Get by Filter
    • Get by Query
    • Get by UID
  • Delete Helper

Installation

Using go get:

go get github.com/dolan-in/dgman

Usage

import(
	"github.com/dolan-in/dgman"
)

Schema Definition

Schemas are defined using Go structs which defines the predicate name from the json tag, indices and directives using the dgraph tag. To define a dgraph node struct, json fields uid and dgraph.type is required.

Node Types

Node types will be inferred from the struct name.

If you need to define a custom name for the node type, you can define it on the dgraph tag on the dgraph.type field.

type CustomNodeType struct {
	UID 	string 		`json:"uid,omitempty"`
	Name 	string 		`json:"name,omitempty"`
	DType	[]string 	`json:"dgraph.type" dgraph:"CustomNodeType"`
}

CreateSchema

Using the CreateSchema function, it will install the schema, and detect schema and index conflicts within the passed structs and with the currently existing schema in the specified Dgraph database.

// User is a node, nodes have a uid and a dgraph.type json field
type User struct {
	UID      string     `json:"uid,omitempty"`
	Name     string     `json:"name,omitempty" dgraph:"index=term"` // use term index 
	Username string     `json:"username,omitempty" dgraph:"index=hash"` // use hash index
	Email    string     `json:"email,omitempty" dgraph:"index=hash upsert"` // use hash index, use upsert directive
	Password string     `json:"password,omitempty"`
	Height   *int       `json:"height,omitempty"`
	Dob      *time.Time `json:"dob,omitempty"` // will be inferred as dateTime schema type
	Status   EnumType   `json:"status,omitempty" dgraph="type=int"`
	Created  time.Time  `json:"created,omitempty" dgraph:"index=day"` // will be inferred as dateTime schema type, with day index
	Mobiles  []string   `json:"mobiles,omitempty"` // will be inferred as using the  [string] schema type, slices with primitive types will all be inferred as lists
	Schools  []School   `json:"schools,omitempty" dgraph:"count reverse"` // defines an edge to other nodes, add count index, add reverse edges
	DType    []string   `json:"dgraph.type,omitempty"`
}

// School is another node, that will be connected to User node using the schools predicate
type School struct {
	UID      string 	`json:"uid,omitempty"`
	Name     string 	`json:"name,omitempty"`
	Location *GeoLoc 	`json:"location,omitempty" dgraph:"type=geo"` // for geo schema type, need to specify explicitly
	DType    []string   `json:"dgraph.type,omitempty"`
}

type GeoLoc struct {
	Type  string    `json:"type"`
	Coord []float64 `json:"coordinates"`
}

func main() {
	d, err := grpc.Dial("localhost:9080", grpc.WithInsecure())
	if err != nil {
		panic(err)
	}

	c := dgo.NewDgraphClient(api.NewDgraphClient(d))

	// create the schema, 
	// it will only install non-existing schema in the specified database
	schema, err := dgman.CreateSchema(c, &User{})
	if err != nil {
		panic(err)
	}
	// Check the generated schema
	fmt.Println(schema)
}

On an empty database, the above code will return the generated type and schema string used to create the schema, logging the conflicting schemas in the process:

2018/12/14 02:23:48 conflicting schema name, already defined as "name: string @index(term) .", trying to define "name: string ."
status: int .
mobiles: [string] .
email: string @index(hash) @upsert .
password: string .
height: int .
dob: datetime .
schools: [uid] @count @reverse .
name: string @index(term) .
username: string @index(hash) .
created: datetime @index(day) .
location: geo .

type School {
        location
        name
}
type User {
        status
        created
        username
        password
        height
        dob
        name
        email
        mobiles
        schools
}

When schema conflicts is detected with the existing schema already installed in the database, it will only log the differences. You would need to manually correct the conflicts by dropping or updating the schema manually.

This may be useful to prevent unnecessary or unwanted re-indexing of your data.

MutateSchema

To overwrite/update index definitions, you can use the MutateSchema function, which will update the schema indexes.

	// update the schema indexes
	schema, err := dgman.MutateSchema(c, &User{})
	if err != nil {
		panic(err)
	}
	// Check the generated schema
	fmt.Println(schema)

Mutate Helpers

Mutate

Using the Mutate function, before sending a mutation, it will marshal a struct into JSON and injecting the Dgraph node type ("dgraph.type" predicate).

user := User{
	Name: "Alexander",
	Email: "alexander@gmail.com",
	Username: "alex123",
}

// Create a transaction with context.Background() as the context
// can be shorthened to dgman.NewTxn(c)
tx := dgman.NewTxnContext(context.Background(), c)
// pass true as the second parameter to commit now
if err := tx.Mutate(&user, true); err != nil {
	panic(err)
}

// UID will be set
fmt.Println(user.UID)

The above will insert a node with the following JSON string, with the field "dgraph.type":["User"] added in:

{"email":"alexander@gmail.com","username":"alex123","dgraph.type":["User"]}

Create (Mutate with Unique Checking)

If you need unique checking for a particular field of a node with a certain node type, e.g: Email of users, you can use the Create function.

To define a field to be unique, add unique in the dgraph tag on the struct definition.

type User struct {
	UID 			string `json:"uid,omitempty"`
	Name 			string `json:"name,omitempty" dgraph:"index=term"`
	Email 			string `json:"email,omitempty" dgraph:"index=hash unique"`
	Username 		string `json:"username,omitempty" dgraph:"index=term unique"`
}

...
	user := User{
		Name: "Alexander",
		Email: "alexander@gmail.com",
		Username: "alex123",
	}

	tx := dgman.NewTxn(c)
	if err := tx.Create(&user, true); err != nil {
		panic(err)
	}
	
	// try to create user with a duplicate email
	duplicateEmail := User{
		Name: "Alexander",
		Email: "alexander@gmail.com",
		Username: "alexa",
	}

	// will return a dgman.UniqueError
	tx = dgman.NewTxnContext(context.Background(), c)
	if err := tx.Create(&duplicateEmail, true); err != nil {
		if uniqueErr, ok := err.(*dgman.UniqueError); ok {
			// check the duplicate field
			fmt.Println(uniqueErr.Field, uniqueErr.Value)
		}
	}

Update (Mutate existing node with Unique Checking)

This is similar to Create, but for existing nodes. So the uid field must be specified.

type User struct {
	UID 			string 		`json:"uid,omitempty"`
	Name 			string 		`json:"name,omitempty"`
	Email 			string 		`json:"email,omitempty" dgraph:"index=hash unique"`
	Username 		string 		`json:"username,omitempty" dgraph:"index=term unique"`
	Dob				time.Time	`json:"dob" dgraph:"index=day"`
}

...
	users := []*User{
		User{
			Name: "Alexander",
			Email: "alexander@gmail.com",
			Username: "alex123",
		},
		User{
			Name: "Fergusso",
			Email: "fergusso@gmail.com",
			Username: "fergusso123",
		},
	}

	tx := dgman.NewTxn(c)
	if err := tx.Create(&users, true); err != nil {
		panic(err)
	}
	
	// try to update the user with existing username
	alexander := users[0]
	alexander.Username = "fergusso123"
	// UID should have a value
	fmt.Println(alexander.UID)

	// will return a dgman.UniqueError
	tx := dgman.NewTxn(c)
	if err := tx.Update(&alexander, true); err != nil {
		if uniqueErr, ok := err.(*dgman.UniqueError); ok {
			// will return duplicate error for username
			fmt.Println(uniqueErr.Field, uniqueErr.Value)
		}
	}

	// try to update the user with non-existing username
	alexander.Username = "wildan"

	tx = dgman.NewTxn(c)
	if err := tx.Update(&alexander, true); err != nil {
		panic(err)
	}

	// should be updated
	fmt.Println(alexander)

Update (Mutate existing node with Unique Checking)

This is similar to Create, but for existing nodes. So the uid field must be specified.

type User struct {
	UID 			string 		`json:"uid,omitempty"`
	Name 			string 		`json:"name,omitempty"`
	Email 			string 		`json:"email,omitempty" dgraph:"index=hash unique"`
	Username 		string 		`json:"username,omitempty" dgraph:"index=term unique"`
	Dob				time.Time	`json:"dob" dgraph:"index=day"`
}

...
	users := []*User{
		User{
			Name: "Alexander",
			Email: "alexander@gmail.com",
			Username: "alex123",
		},
		User{
			Name: "Fergusso",
			Email: "fergusso@gmail.com",
			Username: "fergusso123",
		},
	}

	tx := dgman.NewTxn(c)
	if err := tx.Create(&users, true); err != nil {
		panic(err)
	}
	
	// try to update the user with existing username
	alexander := users[0]
	alexander.Username = "fergusso123"
	// UID should have a value
	fmt.Println(alexander.UID)

	// will return a dgman.UniqueError
	tx = dgman.NewTxn(c)
	if err := tx.Update(&alexander, true); err != nil {
		if uniqueErr, ok := err.(*dgman.UniqueError); ok {
			// will return duplicate error for username
			fmt.Println(uniqueErr.Field, uniqueErr.Value)
		}
	}

	// try to update the user with non-existing username
	alexander.Username = "wildan"

	tx := dgman.NewTxn(c)
	if err := tx.Update(&alexander, true); err != nil {
		panic(err)
	}

	// should be updated
	fmt.Println(alexander)

Upsert

Upsert updates a node if a node with a value of a specified predicate already exists, otherwise insert the node.

type User struct {
	UID 			string 		`json:"uid,omitempty"`
	Name 			string 		`json:"name,omitempty"`
	Email 			string 		`json:"email,omitempty" dgraph:"index=hash unique"`
	Username 		string 		`json:"username,omitempty" dgraph:"index=term unique"`
	Dob				time.Time	`json:"dob" dgraph:"index=day"`
}

...
	users := []*User{
		User{
			Name: "Alexander",
			Email: "alexander@gmail.com",
			Username: "alex123",
		},
		User{
			Name: "Fergusso",
			Email: "fergusso@gmail.com",
			Username: "fergusso123",
		},
	}

	tx := dgman.NewTxn(c)
	if err := tx.Upsert(&users, "email", true); err != nil {
		panic(err)
	}

Create Or Get

CreateOrGet creates a node if a node with a value of a specified predicate does not exist, otherwise return the node.

	users := []*User{
		User{
			Name: "Alexander",
			Email: "alexander@gmail.com",
			Username: "alex123",
		},
		User{
			Name: "Fergusso",
			Email: "fergusso@gmail.com",
			Username: "fergusso123",
		},
	}

	tx := dgman.NewTxn(c)
	if err := tx.CreateOrGet(&users, "email", true); err != nil {
		panic(err)
	}

Query Helpers

Queries and Filters can be constructed by using ordinal parameter markers in query or filter strings, for example $1, $2, which should be safe against injections. Alternatively, you can also pass GraphQL named vars, with the Query.Vars method, although you have to manually convert your data into strings.

Get by Filter

name := "wildanjing"

tx := dgman.NewReadOnlyTxn(c)

user := User{}
// get node with node type `user` that matches filter
err := tx.Get(&user).
	Filter("allofterms(name, $1)", name). // dgraph filter
	All(1). // returns all predicates, expand on 1 level of edge predicates
	Node() // get single node from query
if err != nil {
	if err == dgman.ErrNodeNotFound {
		// node using the specified filter not found
	}
}

// struct will be populated if found
fmt.Println(user)

Get by query

Get by query

tx := dgman.NewReadOnlyTxn(c)

users := []User{}
// get nodes with node type `user` that matches filter
err := tx.Get(&users).
	Query(`{
		uid
		name
		friends @filter(allofterms(name, $1)) {
			uid 
			name
		}
		schools @filter(allofterms(name, $2)) {
			uid
			name
		}
	}`, "wildan", "harvard"). // dgraph query portion (without root function)
	OrderAsc("name"). // ordering ascending by predicate
	OrderDesc("dob"). // multiple ordering is allowed
	First(10). // get first 10 nodes from result
	Nodes() // get all nodes from the prepared query
if err != nil {
}

// slice will be populated if found
fmt.Println(users)

Get by filter query

You can also combine Filter with Query.

name := "wildanjing"
friendName := "wildancok"
schoolUIDs := []string{"0x123", "0x1f"}

tx := dgman.NewReadOnlyTxn(c)

users := []User{}
// get nodes with node type `user` that matches filter
err := tx.Get(&users).
	Filter("allofterms(name, $1)", name).
	Query(`{
		uid
		name
		friends @filter(name, $1) {
			uid 
			name
		}
		schools @filter(uid_in($2)) {
			uid
			name
		}
	}`, friendName, dgman.UIDs(schoolUIDs)). // UIDs is a helper type to parse list of uids as a parameter
	OrderAsc("name"). // ordering ascending by predicate
	OrderDesc("dob"). // multiple ordering is allowed
	First(10). // get first 10 nodes from result
	Nodes() // get all nodes from the prepared query
if err != nil {
}

// slice will be populated if found
fmt.Println(users)

Get by UID

// Get by UID
tx := dgman.NewReadOnlyTxn(c)

user := User{}
if err := tx.Get(&user).UID("0x9cd5").Node(); err != nil {
	if err == dgman.ErrNodeNotFound {
		// node not found
	}
}

// struct will be populated if found
fmt.Println(user)

Scanning Query results

You can alternatively specify a different destination for your query results, by passing it as a parameter to the Node or Nodes.

type checkPassword struct {
	Valid `json:"valid"`	
}

result := &checkPassword{}

tx := dgman.NewReadOnlyTxnContext(ctx, s.c)
err := tx.Get(&User{}). // User here is only to specify the node type
	Filter("eq(email, $1)", email).
	Query(`{ valid: checkpwd(password, $1) }`, password).
	Node(result)

fmt.Println(result.Valid)

Delete Helper

Delete Nodes

Delete helpers can be used to simplify deleting nodes that matches a query, using the same query format as Query Helpers.

tx := dgman.NewTxn(c)

query := `@filter() {
	uid
	expand(_all_) {
		uid
	}
}`
// delete all nodes with node type `user` that matches query
// all edge nodes that are specified in the query will also be deleted
deletedUids, err := tx.Delete(&User{}, true).
	Vars("getUsers($name: string)", map[string]string{"$name": "wildan"}). // function defintion and Graphql variables
	Query(query). // dgraph query portion (without root function)
	OrderAsc("name"). // ordering ascending by predicate
	OrderDesc("dob"). // multiple ordering is allowed
	First(10). // get first 10 nodes from result
	Nodes() // delete all nodes from the prepared query
if err != nil {
}

// check the deleted uids
fmt.Println(deletedUids)

Delete Edges

For deleting edges, you only need to specify node UID, edge predicate, and edge UIDs

tx := dgman.NewTxn(c)
err := tx.Delete(&User{}, true).
	Edge("0x12", "schools", "0x13", "0x14")

If no edge UIDs are specified, all edges of the specified predicate will be deleted.

tx := dgman.NewTxn(c)
err := tx.Delete(&User{}, true).
	Edge("0x12", "schools")